1. Field of the Invention
This invention relates to portable radiotelephone and, more particularly, to a radiotelephone which enables the distance between a microphone unit and a speaker unit to be changed in a predetermined manner.
2. Description of the Related Art
It has been known in the prior art to employ a portable radiotelephone for transmitting voice signals to a telephone base station by radio, that is without interconnecting wires, receiving the voice signals transmitted from the telephone base station, without interconnecting wires and outputting the received signals as a voice output.
The portable radiotelephone is made up of a microphone unit for collecting the voice, a transmitting unit for modulating the voice signals collected by the microphone unit for transmission via a transmission/reception antenna to the telephone base station, a receiving unit for receiving and processing the signals transmitted from the base station via the transmission/reception antenna, and a speaker unit for transducing the voice signals received by the receiving unit into voice.
For portability, the radiotelephone has its transmitting unit inclusive of the microphone unit and its receiving unit inclusive of the speaker unit contained in a one-piece telephone housing or telephone main body. The microphone unit, contained in the telephone housing, is placed so that when the sound radiating surface of the speaker unit, arranged towards one side of the telephone housing, is placed in the vicinity of the user's external ear, the sound collecting surface of the microphone unit is located in the vicinity of the user's mouth. That is, the speaker unit and the microphone unit are arranged within the telephone housing at a distance from each other approximately equal to the distance between the external ear and the mouth of the user. The speaker unit and the microphone unit are placed relative to each other in this manner so that the user may hear the voice received and radiated from the speaker unit while the speech of the user may positively be collected by the microphone unit during signal transmission/reception.
The radiotelephone in which the microphone unit and the speaker unit are contained in this manner within the one-piece housing cannot be reduced sufficiently in size because of the restraint imposed by the distance between the external ear and the mouth of the user, even although attempts have been made to reduce the size of the electronic circuit of the transmitting unit and the receiving unit.
In order to overcome such deficiency, there has been proposed a portable radiotelephone as described for example in JP Patent KOKAI Publication No.2-44843 (laid open on Feb. 14, 1990), corresponding to U.S. Pat. No. 4,845,772. With the radiotelephone, proposed therein, a microphone housing, having the microphone unit contained therein, is pivotally mounted via a hinge at one end of a telephone main body comprising a receiving section inclusive of the speaker unit and an electronic circuit as well as a keypad having a number of dial keys. The microphone housing is rotated via the hinge for folding or unfolding the microphone housing with respect to the telephone main body. The microphone housing has a size selected so as to cover the key pad, having the dial keys, provided on the front surface of the telephone main body, when the microphone housing is folded onto the telephone main body.
With the radiotelephone in which the microphone housing is mounted on the telephone main body via the hinge, the distance between the speaker unit and the microphone unit may be rendered approximately equal to the distance between the external ear and the mouth of the user by unfolding the microphone housing from the main body of the telephone only on the occasion of signal transmission and reception. Since the microphone housing may be folded onto the telephone main body, the radiotelephone may be reduced in size without any limitations imposed by the distance between the external ear and the mouth of the user.
When in the folded state, the radiotelephone is reduced to a pocketable size with convenience for transport. However, for signal transmission and reception, the microphone housing is turned via the hinge so as to be unfolded from the main body of the telephone. Since the microphone housing has a larger surface measure and is moved a larger distance relative to the telephone main body, the microphone housing is susceptible to impact by being impinged upon external objects. If such impact is applied to the microphone housing, it becomes difficult to compensate for the loss of the mechanical strength incurred to the microphone housing. That is, since the microphone housing is simply connected to the main body of the telephone via the hinge, the hinge is stressed concentratedly under the external impact applied from outside to the microphone housing, with the result that the hinge tends to be destructed easily.
Additionally, means for providing electrical connection between the electronic circuit for e.g. the transmitting section provided within the telephone main body and the microphone unit contained in the microphone housing becomes complex in structure because of the complicated construction of an electrical contact responsible for electrical connection and disconnection of rotating portions.
With the radiotelephone in which the microphone housing is collapsibly connected to the telephone housing via the hinge, it may be contemplated to interconnect the electronic circuit section provided in the telephone main body and the microphone unit contained in the microphone housing via a flexible printed circuit board. However, since the flexible printed circuit board is partially introduced into the hinge in such case, the electrical components soldered to the flexible circuit board may tend to be peeled off due to soldering failure connection under mechanical vibrations each time the microphone housing is rotated, thus detracting from operational reliability.